Energy for Muscle Contraction

Direct Phosphorylation

Aerobic Respiration

Anaerobic Glycolysis

Vocabulary

• Aponeurosis: A sheetlike fibrous membrane that binds muscles together or as a means of connecting muscle to bone.

• Motor Unit: A single motor neuron and all the muscle fibers it stimulates.

• Ligament: A sheet or band of tough, fibrous tissue connecting bones or cartilages at a joint

Vocabulary

• Epimyusium: The external sheath of connective tissue surrounding a muscle. (outermost)

• Perimysium: The fibrous sheath enveloping each of the primary bundles of skeletal muscle fibers. (Middle)

• Endomysium: The connective tissue layer surrounding an individual skeletal muscle fiber. (Innermost)

Direct Phosphorylation

• Uses Creatine Phosphate – Found only in muscle – Regenerates ATP

from ADP– CP exhausted in 20

seconds– No Oxygen Used

Aerobic Respiration

• Generates ATP in mitochondria

• Uses Oxygen• Oxidative

Phosphorylation• Glucose is broken

down to CO2 and H2O– 36 ATP per 1 glucose– Slow process– Lasts for hours

Anaerobic Respiration

• Glycolysis uses no oxygen

• Occurs in cytosol• Broken down to pyruvic

acid which is converted to lactic acid when oxygen cannot keep up to demand

• 2 ATP per glucose• 30-60 seconds

Energy Sources

• First: Glucose• Second: Pyruvic

Acid• Third: Fatty Acids

stored in adipose tissue

• Fourth: Amino Acids from protein catabolism

Muscle Fatigue

• Muscle cannot contract even when stimulated

• Weaker and weaker until it stops

• Results from Oxygen debt

• Build up of lactic acid and lack of creatine phosphate and ATP reserves

Oxygen Debt

• Prolonged workouts

• Oxygen uptake can no longer keep up

• Results in rapid or deep breathing

• Muscle may quit entirely

Hitting the Wall

• Bonk• Glycogen depletion• Extreme fatigue• Remedied by

carbohydrates

Movements

• Flexion• Extension• Hyperextension

Movements

• Abduction• Adduction• Circumduction

Movement

• Plantar Flexion• Dorsiflexion

Movement

• Rotation• Medial Rotation• Lateral Rotation

Movement

• Supination• Pronation

Movement

• Inversion • Eversion

Review Sarcomere

More Vocabulary:

• Sarcolemma: Plasma membrane of a muscle cell

• Myofibril: Long organelles that fill the cell and are composed of myofilaments

• Myofilaments: threadlike protein fibers– Thick filaments = Myosin– Thin Filaments = Actin

Muscle Characteristics

• Skeletal: Multinucleate, Striated, Long Thin Cells. Attached to bones. Voluntary

• Cardiac: Branched, Uninucleate, Striated, Intercalated discs. Walls of Heart. Involuntary

• Smooth: Fusiform (tapered), Uninucleate, No striations. Involuntary.

Vocabulary• A Bands = Dark bands of a myofibril• I Bands = Light bands of a myofibril• Z Disc or Z Band= Interruption in the

center of the I Band• M Line: Holds thick filaments together and

can be seen in the center of the H zone• H Zone: Light central area of sarcomere

that lacks actin (also bare zone) this disappears during contraction when fibers overlap

Muscle Contraction Review

1. Motor neuron is stimulated and the action potential travels along the neuron.

Muscle Contraction

2. Acetylcholine is released from the neuron end plate into the neuromuscular junction

Muscle Contraction

3.Acetylcholine diffuses across the neuromuscular junction gap

Muscle Contraction

4. The muscle fiber membrane is stimulated, impulse travels through transverse tubules to sarcoplasmic reticulum

Muscle Contraction

5. Sarcoplaspic reticulum releases Ca+2 into the sarcoplasma

Muscle Contraction

6. Calcium binds to troponin on the actin (thin) filaments allowing myosin (thick) filaments to form cross-bridges

Muscle Contraction

7&8 Power Stroke occurs and repeats as long as calcium is present and the muscle shortens

Muscle Contraction

9. Motor neuron stimulation stops. Cholinesterase causes the breakdown of acetylcholine

Muscle Contraction

10. Calcium ions are pumped out into the sarcoplasmic reticulum using active transport

Muscle Contraction

11& 12 Linkages between actin and myosin are released. The muscle relaxes to its pre-stimulated length

Quiz Tuesday – Muscle Physiology